WASHINGTON — The war authorization that Congress passed after 9/11 will be needed for at least 10 to 20 more years, and can be used to put the United States military on the ground anywhere, from Syria to the Congo to Boston, military officials argued Thursday.

The revelations came during a hearing before the Senate Armed Services Committee and surprised even experts in America’s use of force stemming from the terrorist attacks in 2001.

“This is the most astounding and most astoundingly disturbing hearing that I’ve been to since I’ve been here. You guys have essentially rewritten the Constitution today,” Sen. Angus King (I-Maine) told four senior U.S. military officials who testified about the 2001 Authorization to Use Military Force and what it allows the White House to do.

King and others were stunned by answers to specific questions about where President Barack Obama could use force under the key provision of the AUMF — a 60-word paragraph that targeted those responsible for the 9/11 attacks.

“I learned more in this hearing about the scope of the AUMF than in all of my study in the last four or five years,” said Harvard Law professor Jack Goldsmith, who was called by the committee to offer independent comments on the issue. “I thought I knew what the application [of the AUMF] meant, but I’m less confident now,” he added later.

Concerns emerged largely from questions by senators who approve of an aggressive strategy to combat terrorism, including Sen. Lindsey Graham (R-S.C.), who asked if the AUMF gave Obama the authority to put “boots on the ground” in Yemen or the Congo.